1. Field of the Invention
The present invention relates to an active suspension apparatus for a vehicle and a pump applied thereto, and more particularly, to an active suspension apparatus for a vehicle, which supplies a fluid to an actuator disposed at each wheel of the vehicle using a pump driven by a motor, and a valve thereof.
2. Discussion of Related Art
An active suspension system in a vehicle is a system which detects various inputs from a road surface through sensors, and effectively controls a roll behavior of the vehicle through an electric control unit (ECU) based on the detected inputs.
Specifically, the active suspension system is provided with an actuator which compensates for a displacement of a coil spring connected to a wheel of the vehicle, and constantly maintains a height of the vehicle by appropriately controlling an amount of a fluid supplied to the actuator and detecting a change of a roll and a pitch of the vehicle, and thus enhances ride comfort and a grip force on the road surface.
Furthermore, the active suspension system may allow a driver to set the height of the vehicle through a level control according to a state of the road surface, or may reduce air resistance by reducing the height of the vehicle at a high speed, and thus may enhance driving safety and fuel efficiency.
With regard to the active suspension system, U.S. Pat. No. 6,000,702 discloses a technique in which a spring and a lift-adjustable regulating unit are connected in series, and an amount of a fluid supplied to the lift-adjustable regulating unit is controlled by a proportional control valve.
In such a technique, there is a problem in that the high-priced proportional control valve and hydraulic pump should be used. Also, the hydraulic pump has a structure which is connected to an engine and is always driven, and thus while the engine is working, the pump is always driven to generate a high pressure source, and an excessive capacity which is not required in the system is generated, and fuel economy is lowered by a reduction of an engine output.